Re: GM counter and what next??!

[baumbaug@nosc.mil (Joel T. Baumbaugh)]

     Well, to put my two cents worth in here,

     I've had the same situation(s) occur as the rest of you with
ion  chambers,  but I've also had a comparable situation  with  a
scintillation probe.

     I  was surveying an area around some high voltage lines (208
volt  3  phase) which were within 6 - 7 feet of the  ground,  and
"something"  caused my Ludlum survey meter to wrap the  indicator
needle around the pin at the top of the dial (even on the highest
scale).   My first thought was that the coax cable had a short in
it  (a  problem Ludlum had many years ago), but as I walked  away
the meter quieted down.

     Oh,  Oh, I thought, maybe this is real.   My "faux response"
was  not  directional,  i.e. I could stand in one area (10  x  20
feet)  and  "EVERYWHERE" appeared contaminated!  As I  have  some
pretty  big-  boy sealed sources near by, I was understandably  a
little  nervous until I located the where and why.   My theory is
that  it  is the photomultiplier tube (behind the Na(tl)I)  being
affected  by the EMF as the G.M. probe on the same meter body did
not react in the same way.

     Well,  it  was  a learning experience, and outside  of  some
forehead perspiration, it was a free lesson!


     Joel Baumbaugh  (baumbaug@nosc.mil)
     NRaD
     San Diego, CA


     Std  disclaimer - my boss, the Navy and the Federal govt. do
not necessary agree with anything I type here....